1. Field of the Invention
The invention relates to an electric connector including a male connector having a cylindrical main portion, and a female connector having a hole into which the main portion is fit.
2. Description of the Related Art
An electric connector such as a connector used in a glow plug acting as a spark plug or a pre-heater plug in an engine, and a connector used for electrically connecting a combustion pressure sensor to a wire harness, generally includes a cylindrical male connector. Since a portion of the male connector through which the male connector is fit into the female connector is rotation-symmetrical to the female connector, the male connector can be fit into the female connector, even if the male connector rotates in any direction about an axis thereof, ensuring that the male connector can be manually fit into the female connector even in invisible condition.
FIG. 23 is a perspective view of a plug connector and a receptacle connector both suggested in Japanese Patent Application Publication No. H9(1997)-35825. The plug connector 1000 includes a plug insulator 1001 in the rotation-symmetric form, and a plurality of plug contacts 1002 each disposed at different distances from a distal end of the plug insulator 1001. The receptacle connector 1010 includes a receptacle insulator formed with a fitting hole 1011 into which the plug insulator 1001 is fit, and a plurality of receptacle contacts 1012 disposed at an inner surface of the fitting hole 1011.
FIG. 24A is a cross-sectional view of a glow plug suggested in Japanese Patent Application Publication No. 2005-207730, and FIG. 24B is a perspective view of the glow plug illustrated in FIG. 24A.
The illustrated glow plug includes an electrically insulating casing 1100, a sensor contact 1101 disposed on an inner surface of the casing 1100 for making contact with a sensor (not illustrated) when the male and female connectors are fit into each other, sensor contacts 1102 and 1103 disposed on an outer surface of the casing 1100, and a contact 1104 disposed at a center of the casing 1100 and making contact with a contact (not illustrated) of a heater used for heating the glow plug when the male and female connectors are fit into each other.
In the conventional connector illustrated in FIG. 23, since the receptacle contacts 1012 of the receptacle connector 1010 making contact with the plug contacts 1002 of the plug connector 1000 are exposed at an inner surface of the fitting hole 1011, the receptacle contacts 1012 of the receptacle connector 1010 may be damaged, if the plug insulator 1001 is inserted into the fitting hole 1011 of the receptacle connector 1010 with an axis of the plug connector 1000 being inclined relative to an axis of the fitting hole 1011, or if the plug insulator 1001 is inserted obliquely into the fitting hole 1011 of the receptacle connector 1010, varying a direction in which the plug connector 1000 is inclined.
In the conventional glow plug illustrated in FIGS. 24A and 24B, since the contact 1104 is disposed at a center of the casing 1100, if the glow plug is inserted into a connector (not illustrated) with an axis of the glow plug being inclined, the contact 1104 makes frictional contact with an inner surface of a female connector, and may be damaged. Furthermore, since the sensor contact 1101 is disposed inside of the casing 1100, the contact 1101 makes frictional contact with an outer surface of a female connector, and may be damaged. If the contacts 1101 and 1104 of the glow plug as a male connector were damaged, reliability to electrical connection between the glow plug and a female connector would be deteriorated.